The present invention concerns novel alkaline hemiesters of bis(hydroxy-4-phenyl)-alkylphosphonic acids of the general formula (I): ##STR2## in which: R is a cyclohexyl or aliphatic hydrocarbon radical having 1 to 6 carbon atoms,
n is equal to 0, 1, 2 or 3, and PA1 M is an alkaline metal e.g. lithium, sodium or potassium. PA1 R.sub.1 and R.sub.2 are an C.sub.1 to C.sub.6 aliphatic hydrocarbon radical, or of dialkyl phosphonates of bis-(hydroxy-4-phenyl)-1,1-ethyl, already known in the art, having the general formula (III): ##STR4## which are described along with their preparation in U.S. Pat. No. 3,702,879.
These novel products may be obtained from novel dialkyl phosphonates of bis-(hydroxy-4-phenyl)-alkyl having the general formula (II): ##STR3## in which: n is an integer equal to 1, 2 or 3,
The alkaline hemiesters according to the present invention may be used as stabilisers antioxidants, or fire resisting agents for organic materials and specially plastic materials. Their difunctional phenolic character allows them to be used as polycondensation monomer or comonomer leading to such polymers as polyethers, polycarbonates, epoxy resins obtained from diphenols.
The presence of phosphonic ion can give to such plastic materials internal characteristics of stabilization, fire resistance, ion exchange or complexing agents for the metals.
Phosphonic diesters having a structure similar to that of formula (II) were described by Spivack in Belgium Pat. No. 750,593. However the diesters prepared by Spivack comprise several aliphatic or alicyclic substituents on the phenyl nucleii thus creating a hindered structure which renders these products unsuitable for polycondensation.
The alkaline hemiesters derived from formulae (II) and (III) comprise no substituent on the phenyl nuclei and therefore they can be used as polycondensation monomer with the aim of obtaining plastic material carrying phosphonic functions of the formula: ##STR5##
Among the hemiesters to be obtained can be cited inter alia:
sodium and methyl phosphonate of bis-(hydroxy-4-phenyl)-1,1-ethyl,
potassium and methyl phosphonate of bis-(hydroxy-4-phenyl)-1,1-ethyl,
sodium and methyl phosphonate of bis-(hydroxy-4-phenyl)-2,2-propyl,
potassium and methyl phosphonate of bis-(hydroxy-4-phenyl)-2,2-propyl,
sodium and methyl phosphonate of bis-(hydroxy-4-phenyl)-3,3-butyl.
These alkaline phosphonic hemiesters can be obtained from the diesters of the corresponding bis-(hydroxy-4-phenyl)-alkylphosphonic acids through treating the latter with either an alcohol solution of 10 to 20% by weight alkaline hydroxide, in a molar ratio alkaline hydroxide/diester of 3.2 to 3.5 or by a ketonic solution saturated with alkaline iodide, the molar ratio NaI/diester being 1.5 to 2.5.
A way of preparing alkaline hemiesters according to the present invention consists in treating at reflux during 24 hours the corresponding dialkyl phosphonates of bis-(hydroxy-4-phenyl)-alkyl by a ketonic solution of sodium iodide.
The precipitated hemiester is isolated and purified by filtration, washed with solvent and dried under vacuum.
Another way of preparing the alkaline hemiesters according to the present invention consists in treating the corresponding dialkylphosphonate of bis-(hydroxy-4-phenyl)-alkyl by an alcohol solution of NaOH at reflux during 10 to 24 hours; the precipitated sodium chloride is filtered and the solvent is evaporated to dryness under a vacuum of 0.5 to 2 mm.Hg.
U.S. Pat. No. 3,702,879 describes the preparation of phosphonates of bis-(hydroxy-4-phenyl)-1.1-ethyl from a .alpha.-ketophosphonate on which phenol has been made to react in the presence of a Lewis acid.
The novel phosphonic diesters of bis-(hydroxy-4-phenyl)-propyl, butyl or pentyl may be obtained by reaction of the .beta.,.gamma. or .delta.-ketophosphonates on phenol in the presence of a Lewis acid, preferably boron trifluoride, according to the following reaction scheme: ##STR6##
As ketophosphonic acid diesters, also called oxoalkyl phosphonate may be used, for example:
dimethyl phosphonate of oxo-2-propyl,
diethyl phosphonate of oxo-2-propyl,
diethyl phosphonate of oxo-3-butyl,
diethyl phosphonate of oxo-4-pentyl,
dicyclohexyl phosphonate of oxo-2-propyl.
To prepare the dialkyl phosphonates of bis-(hydroxy-4-phenyl)-alkyl according to the present invention, an oxo-alkyl phosphonate is mixed with phenol in a molar ratio phenol/oxo-alkyl phosphonate of 4 to 8 and the boron trifluoride is caused to bubble in this mixture until saturation while maintaining the temperature between 10.degree. and 30.degree. C., and preferably between 15.degree. and 25.degree. C.; then the temperature is raised to about 40.degree. to 50.degree. C. and the condensation reaction occurs at atmospheric pressure during 30 to 60 minutes.
When the reaction is completed the product is diluted in acetic acid and the mixture is added with water which leads to the precipitation of a slowly hardening oily product. The solidified product is washed with water, centrifuged and dried. The obtained powder is purified by crystallisation in a solvent or a mixture of suitable solvents. To obtain the corresponding alkaline hemiesters the bis-(hydroxy-4-phenyl)-alkyl-phosphonate obtained is treated by an alcohol solution of NaOH or KOH at reflux during 10 to 24 hours.
Afterwards, the reaction mixture is neutralised with HCl, until pH=7 and concentrated under reduced pressure.
The precipitated sodium chloride is filtered and the evaporation of the filtrate is completed to dryness under vacuum of 1 mm.Hg.
The products are identified by elementary analysis, infrared spectrum and NMR spectrum.
The following examples are given by way of illustration without in any way limiting the present invention.